A sketch for painting written in processing 3.x
(External libraries used: none)

Tools
Pencil
Line
Rectangle/Square
Ellipse/Circle
Vernice
Ink Pen
Stamp
Mixer (Smudge)
DynaDraw
Filler
Clone
Web Pen
Selection
Stencil
Confetti
Shape
Alpha Paint
RGB Paint
HSB Paint
ARGB
BACKground
Eraser

Features
Open and Save drawing
Import/Export images
Layers with transparency, reorder, save, merge, delete, show/hide
Undo/Redo
Grid with Snap
X,Y mirror drawing
RGB and HSB color selector
Zoom
Keyboard shortcuts
Manual (Italian/English)